High HP loss with high stall!

Hey guys, I need some help. Background: I'm running a 383 with 16# Vortech full manual TH400 built by SR7 Performance(Las Vegas) and a TCS converter. The converter was supposed to stall at 2800-3000 RPM. I took it to the dyno and we saw a very disappointing 308 RWHP and 389 FT/LB torque. The dyno graph's showed HP and Torque were falling off at about 4500-5000 RPM and the higher the RPM got the worse they dropped off. We only saw 100 MPH@6000 RPM! The stall was actually flashing at around 4500 with the blower and 3800 w/o the blower. We were expecting to see around 600 RWHP and over 500 FT/LB of torque, that's a 300 HP loss! They said the HP was blowing right through the converter. Am I losing all the power due to the converter or because I'm running 2.73's(for now, saving up for Moser 9" with 3.73's or 4.11's). Also the 1-2 shift is very fast and firm, but the 2-3 shift isn't. Both the engine and driveline has aroung 150 miles on them. Help! Any comment's and suggestions are appreciated, thanks Rob.

it sounds like the motor is driving right through the converter. wayy too loose. I'd call your converter provider and see what happened. Sounds like they underestimated your motor power or something.

You might be losing a little bit due to the small gears. I'd put 3.73's in it since your a power adder app.

I did, He said he would tighten up the converter but that I'd probably want it re-stalled once I put in the new rearend. I'm trying to figure out what my options are, restall the converter now or wait for new rear. Is that big of a HP loss feasible? What stall should I shoot for? Thank's for the post.

I have a TH400 with a non-locking converter. The converter flashes to 5,000rpm under 800 lb-ft load. Since I have both chassis dyno and engine dyno pulls, available, I was able to calculate the HP loss through the drivetain, with both the TH400 and with a T56.

At 765 flywheel HP, the losses were:

T56, Street Twin, chrome moly DS, 3.73 12-bolt: 673 rwHP, 12.1% drivetrain loss

TH400, non-locking converter, chrome moly DS, 4.11 12-bolt: 602 rwHP, 21.3% drivetrain loss.

I've seen numbers as high as 25% for the TH400..... but you would have to be losing more than 50% to get the numbers you are indicating.

Yeah, thats what I fugured. The trans shop want's to see what the converter flashes at with new gears and then go from there. They said that with that high of a rearend gear the engine is blowing through the converter and I'm not getting the HP to the wheels. Does this sound right? With my combo I should be seeing upwards of 600 RWHP shouldn't I? Can a TC cause this much of a problem with the gears I have now?

Keep in mind that flash stall won't really change with a gear change. Drive away stall will and should be lower with the easier to move the car lower gears. In your case though it sounds as if there is no torque multiplication happening at stall which COULD be due to a bad converter buildup. Some small companies grind on the stator which can destroy torque multiplication but still technically give you stall which does nothing but heat fluid. Now I'm not saying the converter is faulty at all, it just something that can happen, after all most converters are welded shut only to be seen by the builder.

You mentioned 100 mph at 6000 rpm. I'm going to just assume a 26" tire and figure your slippage.
The formula for a stick or 100% lockup is: MPH*GEAR_RATIO*336 / TIRE DIAMETER=RPM

In your case 100 * 2.73 * 336 / 26 (guess) = 3528 RPM

3528 / 6000 = .59 or 59% ....41% slippage!! This my friend is very bad. A good performance converter should only slip 10% or so at "lockup" (when the vehicle has accellerated past the stall point). In fact it is possible to build a 9" converter that will have only 5-8% slippage behind 2500+ hp in a 3000 lb car.

While your high gear can hurt converter efficiency, car weight is a non issue on a chassis dyno. You need to talk to your builder again. I'd bet accelleration is pretty bad from a stop.

I am not sure what is happening on a chassis dyno when the converter is being "overpowered" but I have seen it. With the first converter after switching from a T56 to a TH400 there was a difference of ~150rwhp. With a better matched converter, it was ~90hp. I never tried the original converter under full load on the street or track, but I imagine it would generated so much heat as to damage the tranny and can't imagine the performance would have been any good. After all, the dyno (Dynojet) has less inertia than the car.

You need a different converter. Of course, the tranny could also be slipping.......

Rich

Thanks for the replies guys. I talked to the manufacturer, TCS Performance. They have made me feel reassured that they will make the converter right. For now I'm going to throw in a set of 4.10's in the stock 10 bolt and run it till it scatters(then get the Moser 9"). At least then I won't have to worry about cooking the TC or trans. I looked at TCS's website, they seem to be a good company. Has anyone else had any experience with them? This converter is a really nice looking piece, but looks aren't everything. Would these symptems also explain the soft shift into 3rd? I went to a TH400 beacause I fried 2 sets of 3-4 clutches in my 4L60E and was tired of putting more money into that trans.

I have heard that a stall converter will make a shift seem softer. I kind of have the same problem with my car tho mine is not near the power level u have. My 1-2 is hard as hell and makes my cd player skip, but 2-3 is ALOT softer. I am guessing in your case with the bad converter it may make it potentially worse, just my opinion. Peace, Dustin.

You have torque converter problems. The rear end gear will effect stall some, bit not to the degree of what you are talking about, The torque is the sole culprit here. The transmission shifting to firm on the 1-2, & too soft on the 2-3 is in the setup of the clutches, feed hole sizes, & the accumulation setup or lack there of that effects the shift feel on this transmission. Too firm of a 1-2 shift can break the case lugs on the intermediate clutch pack, and/or roll over the 34 element sprag (you lose 2nd gear).

I never tried the original converter under full load on the street or track, but I imagine it would generated so much heat as to damage the tranny and can't imagine the performance would have been any good. After all, the dyno (Dynojet) has less inertia than the car.
Rich

Dynojets have 5400lb rollers, they put a heavier load on the car than driving it on the street will, and yes have more inertia.

I believe the rollers have less inertia than the car. On the dyno, 50-150 takes <5 seconds and while I never measured that on the road, I know it's not THAT fast. By "inertia" I also mean to include aerodynamic drag.

Rich

So even if I change gears its still going to blow right through the TC? The 1-2 shift is not too hard, seems just right. The 2-3 shift is fast but not firm like the 1-2 shift. Has anybody else delt with TCS Perf converters and SR7 Perf transmissions before? SR7 is in Vegas and came highly recommended by Combination Motorsports which everyone on this board knows is a highly reguarded company and SR7 recommended TCS. So it sounds like you guys are telling me no matter what I'm going to have to send back the converter and have it re-stalled. What should I shoot for on the stall to get the most out of my car. The car will see very few street miles, maybe just cruise nights once in a while, but mostly for the track now. Thanks guys, as always a big help. How am I on my HP and Torque estimates?

well I have had two SR7 transmissions now, one blew after 14-15 months on a stock SS Impala. Daily driving freeway, stop and go. THATS IT. No racing, no donuts etc. I was working 60+ hours a week, I didn't have time to be doing all that stuff.
At any rate SR7 warrantied the first one, charged for parts, I bought a converter through them as mine had Died with the first trans. So later one, a few months go by, and wam, no 4th gear. Get the trans shipped back at my expense, fixed, sent back, reinstalled and the converter is giving me the p1870 code(converter slipping).
So I drive the damn thing out the vegas, from LA. Drop it off fly, back and wait. Its finally, "fixed" so I fly back pick it up, as I'm driving back I get the damn code again! But I have work the next day and I'm already halfway there. So I continue to drive it, and clear the code when it comes about. I replace the VSS and wiring, per request of the builder. This does nothing, the problem persists. I flush the fluid, still does nothing.
*apparent the trans was NOT slipping, but the line pressure was programmed too high, so on WOT it could not shift*

Update: new trans from SR7 going into the car with my 383 all ready to go. Gonna good to have the car running again!